MIAMI -- A lead hijacker in the 2001 terrorist attacks was stopped at Miami International Airport for questioning after an apparent organizing meeting in Spain but was allowed to enter the United States, investigators determined.

Details of the hijackers' movements in the months leading up to the attacks were outlined in a 858-page report released Thursday after a joint congressional inquiry.

Mohamed Atta left Miami for Madrid in January 2001 and is believed to have met with an al-Qaida operative to get information on other hijackers who began arriving in the United States five months later, the report said.

On his return, Atta was pulled out of the line of new arrivals at the airport and questioned about his flight lessons. He was cleared because his pilot student visa application was pending.

Hijackers who played supporting roles in the attacks "divided between Florida and New York before moving to three staging areas," the report said. Nine flew to Florida, five through Miami and four via Orlando.

Atta is suspected of leaving Florida again in April 2001 to meet an Iraqi agent in Prague. The report quotes CIA Director George Tenet as saying the secret trip was possible but not corroborated.

His last known trip out of the country was in July 2001, when he flew from Miami to Zurich, Switzerland, and then to Spain. Investigators believe he might have met with Ramzi bin al-Shibh, a suspected organizer and money supplier.

The Yemeni man, who was Atta's roommate in Hamburg, Germany, may have been cast as a hijacker but failed to get a U.S. visa. He was captured in Pakistan last September and is in U.S. custody at an undisclosed location.

Ziad Jarrah, another Florida-based hijacker, tried to enroll bin al-Shibh in the Florida Flight Training Center in Venice where Jarrah was taking lessons. Bin al-Shibh wired $2,200 to the fight school for tuition Aug. 15, 2000, the report said. He then unsuccessfully attempted to obtain a U.S. visa, three times in Germany and once in Yemen.

After bin al-Shibh was turned down, Zakariya Essabar, another old Atta roommate from Hamburg, failed twice to get a U.S. visa to travel to Florida and join Atta and Marwan al-Shehhi, the third hijacker to operate from Florida.

Al-Shehhi flew to Cairo, visited Atta's father and returned May 2, 2001, with Atta's international driver's license. The report doesn't say why the license was needed, but Atta was cited by Broward County sheriff's deputies for driving without a license a week before.

Hijacker Hani Hanjour, who spent most of his time in California and Arizona in the months before the attacks, lived in Florida for about a month in 1996 while studying English. When he returned to the United States in late 2000, he stayed in Florida for a month before moving west.

Hijackers Atta, al-Shehhi, Hanjour, Nawaf al-Hazmi and Khalid al-Mihdhar may have had contact with a total of 14 people in FBI counterterrorism or counterintelligence investigations before the attacks, the report said.

At least 15 of the 19 hijackers had Florida connections and several took flight lessons at different schools throughout the state, including two of the terrorists believed to be at the controls of the two jetliners that struck and destroyed the World Trade Center towers. Thirteen of the hijackers also obtained Florida licenses or ID cards.